Most transducer materials which are suitable for use at frequencies suitable for underwater sound transmission are weaker in tension than they are in compression. Typically, these materials can withstand and operate at compression values of over 10,000 psi but will fracture with only 2,000 psi tension. This is true of piezoelectric ceramic materials and magnetostrictive rare earth irons such as Terfenol D (Tb.sub.0.3 Dy.sub.0.7 Fe.sub.2). In prior art transducer designs, the need for precompressing the transducer material is satisfied by the use of a high strength steel bolt, or fiberglass wrapping under tension, or both. Typical precompression values of 4,000 to 5,000 psi allows operation with an alternating stress field of approximately 4,000 psi maximum. The precompression also strengthens the transducer material against mechanical shock and vibration.
In some applications requiring precompression of transducer materials, the stress bolts are too cumbersome and too rigid to be used effectively and can lead to a severe reduction in the effective coupling coefficient of the transducer. The use of the fiberglass wrapping technique for precompression is also not feasible in some configurations of transducer materials.